Very fast weight loss is what many people looking to lose weight hope to accomplish. So they go on a very low calorie diet, which is the fastest way to lose weight.
But this is a big mistake, as there are four major problems with very low calorie diets.
The first problem is that very low calorie diets, especially very low carbohydrate diets, are dehydrating. This means that when you drastically reduce your calories you're going to lose a lot of water. This is why the initial weight loss on very low calorie diets is deceiving, because you lose more water than you do body fat.
The second problem is that very low calorie diets cause your metabolism to slow down, and this causes you to lose lean muscle mass. When you drastically reduce your calories, your body thinks it's being starved. Your body reacts to this perceived starvation by slowing down your metabolism. Since muscle is very metabolically active tissue, your body starts using lean muscle mass for energy instead of body fat, which is metabolically inactive tissue.
